CONCERNED residents have sighted an alien species of infected crayfish in the River Skerne in Darlington.

The American signal crayfish are known to destroy populations of river fauna and flora, eating fish, fish eggs, other crayfish and even their own young.

The ferocious species were recently spotted in the river near the Town Hall, South Park and along Victoria Embankment.

Darlington resident David Race first saw one as he crossed the river via the foot bridge behind St Cuthbert's church.

He said: "I saw a strange movement that caught my eye in the river.

"I thought it was a leaf but it was actually a crayfish.

"It was as big as my hand and had a white joint near the claw.

"They are spreading all over the country and it's actually quite serious.

"They eat other crayfish and and spread disease as well.

"When they get to such large numbers they can even destroy the riverbank through burrowing."

The signal crayfish first made it across from America to the UK in 1976.

They have since become widespread across the country and are not only vicious feeders but also carriers of crayfish plague which has put the native white-clawed crayfish on the endangered list.

The invading species were also sighted in River Gaunless which runs from Copley to Bishop Auckland in August of this year.

Conservationists at the time said it was very bad news for the river ecosystem and the native invertebrates.

The Environment Agency’s Richard Jenkins, said: “We are aware of American signal crayfish in the River Skerne and would ask people to continue to report sightings to us.

“We can all do our best to contain them and stop them from spreading, to help protect our native crayfish and other wildlife.

“We’re calling on all river users and anglers who fish the River Skerne and other rivers in the North East to help us by checking, cleaning and drying all their fishing tackle and footwear thoroughly, so that we can halt the spread of the disease that the signal crayfish carry.

“In the North-East we still have native populations which are holding out against any invasion, and we want to keep it that way.”